Forum Discussion
GROUPBY Context Transition
RobertSlattery- I may be off-base here but I believe you have a fundamental misunderstanding of how measures function. For measures in DAX, the starting filter context is ALWAYS the context of the visual. So, if you use a measure in a single row, that's the starting context of the measure unless you change it by wrapping the calculation in a CALCULATE or CALCULATETABLE and using something like an ALL, ALLEXCEPT or other type of filter that fundamental and specifically changes the original filter context.
Your first calculation doesn't do any of that. Your first calculation starts with a filter context of a single row. So, that is the starting filter for the GROUPBY, which is not a context/filter changing function. It is just going to do it's thing on whatever data it has access to based upon the starting context/filter.
Therefore, it is really, really difficult to see exactly what is going on with your functions with what I would consider 1/3rd of the critical information. You have presented the calculations, which is good but we are missing the context in which you are placing them (your use of them in visuals, what visuals, what other information is around them, etc.) And the actual data or a sample of data that is being used so that we can replicate the issue/behavior without recreating it all.
RobertSlattery- I may be off-base here but I believe you have a fundamental misunderstanding of how measures function. For measures in DAX, the starting filter context is ALWAYS the context of the visual. So, if you use a measure in a single row, that's the starting context of the measure unless you change it by wrapping the calculation in a CALCULATE or CALCULATETABLE and using something like an ALL, ALLEXCEPT or other type of filter that fundamental and specifically changes the original filter context.
Your first calculation doesn't do any of that. Your first calculation starts with a filter context of a single row. So, that is the starting filter for the GROUPBY, which is not a context/filter changing function. It is just going to do it's thing on whatever data it has access to based upon the starting context/filter.
Therefore, it is really, really difficult to see exactly what is going on with your functions with what I would consider 1/3rd of the critical information. You have presented the calculations, which is good but we are missing the context in which you are placing them (your use of them in visuals, what visuals, what other information is around them, etc.) And the actual data or a sample of data that is being used so that we can replicate the issue/behavior without recreating it all.
Youre right Greg_Deckler, the context is there regardless of the Calculate. I'm a bit confused about this, given all the mysterious handwaving about Calculate efecting a ~Context Transition~. SMH.
OK, thanks again.
Correct, the CALCULATE just gives you the option of changing the context/filters of the calculation. So, if you use something like FILTER then you are taking the existing context from the visual that is coming into the calculation and becoming more selective. Alternatively, you can use things like ALL and ALLEXCEPT to remove context and then, potentially add context/filters back to it.
Understanding DAX hinges on understanding the concept of context and paying close attention to the context in which the code is running.